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.TH STDDEF.H 3HEAD "Jan 14, 2015"
.SH NAME
stddef.h, stddef \- standard type definitions
.SH SYNOPSIS
.LP
.nf
#include <\fBstddef.h\fR>
.fi

.SH DESCRIPTION
.LP
The <\fBstddef.h\fR> header defines the following macros:
.sp
.ne 2
.na
\fB\fBNULL\fR\fR
.ad
.sp .6
.RS 4n
Null pointer constant.
.RE

.sp
.ne 2
.na
\fB\fBoffsetof(type, member-designator)\fR\fR
.ad
.sp .6
.RS 4n
Integer constant expression of type \fBsize_t\fR, the value of which is the
offset in bytes to the structure member (\fBmember-designator\fR), from the
beginning of its structure (\fBtype\fR).
.RE

.sp
.LP
The <\fBstddef.h\fR> header defines the following types:
.sp
.ne 2
.na
\fB\fBptrdiff_t\fR\fR
.ad
.RS 13n
Signed integer type of the result of subtracting two pointers.
.RE

.sp
.ne 2
.na
\fB\fBwchar_t\fR\fR
.ad
.RS 13n
Integer type whose range of values can represent distinct wide-character codes
for all members of the largest character set specified among the locales
supported by the compilation environment: the null character has the code value
0 and each member of the portable character set has a code value equal to its
value when used as the lone character in an integer character constant.
.RE

.sp
.ne 2
.na
\fB\fBsize_t\fR\fR
.ad
.RS 13n
Unsigned integer type of the result of the \fBsizeof\fR operator.
.RE

.sp
.ne 2
.na
.B max_align_t
.ad
.RS 13n
A type that represents the maximum alignment supported by the platform.
The type may or may not be an integer type, it may or may not be signed,
no assumptions should be made, other than that it has the maximum
fundamental alignment of the platform.
.RE

.sp
.LP
The implementation supports one or more programming environments in which the
widths of \fBptrdiff_t\fR, \fBsize_t\fR, and \fBwchar_t\fR are no greater than
the width of type \fBlong\fR. The names of these programming environments can
be obtained using the \fBconfstr\fR(3C) function or the \fBgetconf\fR(1)
utility.
.SH ATTRIBUTES
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
.TE

.SH SEE ALSO
.LP
.BR getconf (1),
.BR confstr (3C),
.BR types.h (3HEAD),
.BR wchar.h (3HEAD),
.BR attributes (7),
.BR standards (7)
